KENNEDY SPACE CENTER, FLA. - The orbiter Discovery rolls over to the Vehicle Assembly Building (VAB), marking a major milestone in the march to Return to Flight. First motion was at 1:29 a.m. EST. Inside the VAB, Discovery will be mated to the External Tank/Solid Rocket Booster assembly for Return to Flight mission STS-114. After all umbilicals have been connected, workers will perform an electrical and mechanical verification of the mated interfaces to verify all critical vehicle connections. A Space Shuttle interface test is performed to verify vehicle interfaces and vehicle-to-ground interfaces. The launch processing system is used to control and monitor orbiter systems as required. Space Shuttle Discovery will roll out to Launch Pad 39B approximately one week after the rollover to the VAB. The launch window for mission STS-114 is May 15 to June 3.